An excellent film showing how telegrams were sent
Note: This was England in the 1940's - BT is British Telecom (telephone monopoly) and GPO is the Government Post Office.
These machines were driven by synchronous motors depending on the power grid to provide the same speed of rotation at Point A and Point B.
A later unit - Teletype's Keyboard Send and Receive Model 33 (KSR-33) were used by hackers as the first cheap input devices and printers. I used to have a couple of them. Lucky sods that could afford the automatic version (ASR-33) got a unit with a paper tape drive for storing programs and reading them in later. I got one of those a bit later and then graduated to a DECwriter (way faster and lower maintenance) and finally graduated to a Daisy Wheel printer. Got my first laser printer a few years later (1980 or so). It has been a fun ride!
I had a military tt7/FG, the militarized version of the Model 19. It had a multi-voltage, multi-frequency power supply for overseas use. Since the frequency varies from one country to another, this one had DC motors and you had to set the speed using a special tuning fork.
These things are a model of complexity. Seeing one at work is revelatory.
MC